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Smart Formulating Journal Issue 9 | April 2012
High technology in the store cupboardPage 9
TEGO® AddBond – the Multitasking Adhesion Promoter! Page 7
Widening the Scope for Matting Solvent-Free UV-Cured Coatings Page 6
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EditorialDear Readers,Dear Customers and Evonik Business Partners,
What you have before you right now is the ninth issue of our customer magazine for the paints and coatings market, in which we have again provided you with an update on the latest developments at Evonik.
“Evonik is specialty chemicals”. That was my message to you in the previous issue of our SF Journal. It is based on this strategic policy principle that Evonik has launched an ambitious growth program for its activities in the chemicals fi eld. That program is already bearing discernible fruits in many areas of our enterprise operations. In a move, for example, to lend added strength to our activities in the coatings market–one of the focus markets for Evonik growth–we concluded the acquisition of Hanse Chemie AG and Nanoresins AG in 2011.
Acquisition is one course we have been taking, but Evonik also aims, more importantly, to achieve organic growth, in the pursuit of which we have mapped out other key avenues of enterprise development. In Shanghai, for exam-ple, we are in the process of building our fi � h isophorone production line. In addition, we are building two coatings development labs in Shanghai and Singapore as well. Each of these planned investments refl ects our unequivocal acknowledgement of the growing signifi cance which the
markets of Asia enjoy. We will by no means, of course, be neglecting our traditional markets, and will be mak-ing further targeted investments in these markets, too. In Essen, for example, we are currently building a new inno-vation center for our Coatings & Additives Business Unit.
What all these investments have in common is that they help us to achieve better market proximity and closer proximity to you, our customers. Optimized proximity is an imperative in the context of our aim to achieve improved resource efficiency. For it is only on a basis of trusting and affi rmative dialog that new, eco-friendly, customized solutions will evolve. Thus, we are investing not only in new products and facilities, but equally in our network of experts who will continue to work together with you across our various business units to consolidate our Know-How in the Area of Competence “Coating & Bonding Technologies”. We wish for you to perceive us as a partner and problem solver with whom you are eager to collabo-rate on achieving continued success for your business.
In this issue of the SF Journal we illustrate how we are able to fi nd solutions to the problems our customers encounter. We report, for example, on how SILIKOPUR® 8080 can substantially improve abrasion
Dr. Thomas Haeberle Member of the Board of Management of Evonik Industries
Because we love your problems, we’re the perfect partner when it comes to coatings. “We love your problems.” That’s what we call our international market initiative, and it will also be part of our presence at a number of coatings shows. But the message is far more than a campaign; it’s an expression of how we see ourselves. We love your problems, and that’s why we work with you, channeling all our commitment and creativity into developing solutions for your coating issues.
resistance in air-drying PU dispersions and how ACEMATT® can mat UV-curing coatings. We also report on silica nano-composites, solvent-free deaerators for high solid coatings, and much, much more.
In addition to providing information on all these themes in this latest issue of the SF Journal, I invite you to actively engage in further discussions and collaboration with us in pursuit of the goal as proclaimed by the motto of this year’s American Coatings Show: “Preparing for Future Demands”.
Kind regards
2
Smart Formulating Journal | Issue 9 | April 2012
DEGALAN® Resins – Excellent Base for Formulating Intumescent PaintsIntumescent paints are functional coatings that expand their volume under heat building a foam. This foam works as heat shield protecting the substrates from direct fi re contact and thus delaying the spread of fi re. More time for the rescue of people is available and protection against massive damages. Essential for high protection is a uni-form foam structure and height. Typically intumescent paints are based on a polymer, a catalyst (e. g. aluminum
phosphate), a carbon source (e. g. pentaerythrit) and a foaming agent (e. g. melamine). DEGALAN® resins based on thermoplastic (meth)acrylics are ideal binders for intu-mescent paints as they simply do not infl uence the foam development.
In fact the DEGALAN® polymers shield the water sen-sitive paint ingredients, reduce mechanical impacts, pro-mote adhesion on several substrates and give excellent
UV-resistance. Thus DEGALAN® resins help in formulat-ing effi cient intumescent coatings.
ContactAndreas Olschewski
Coatings with Fish EyesWhen spraying modern high-solids coatings, there are o� en problems like blisters, fi sh eyes and other defects. The biggest challenge was to fi nd an additive that reliably prevents these problems while displaying good compat-ibility. To solve this problem, we worked closely with a number of our customers. As a result of our working together, two new deaerators for high solids coatings have been developed, TEGO® Airex 990 and TEGO® Airex 991, that can reliably prevent foam / blister formation even in
high fi lm thicknesses and give our customers greater free-dom in choosing the type and quantity of solvents for their coating.
Cans in Danger The inner coating of a food can has a lot to put up with. During forming as part of the manufacturing process, it has to be fl exible and yet still retain its high hardness. But that’s only the start. It then has to withstand the high temperatures of the sterilization process and display last-ing resistance to aggressive contents such as acetic acid in order to prevent metal particles getting into the food.
That’s a lot of work for a coating and, above all, for the binder. The solution: DYNAPOL®. Our polyester resins off er optimum protection, high fl exibility in the manufac-turing process, a level of temperature resistance that can withstand sterilization at 130 degrees Celsius, and high resistance to aggressive contents.
Film Shrinkage Under the SpotlightThe absence of a solvent o� en causes problems in the matting of UV-curable coatings because the necessary
fi lm shrinkage does not take place and has to be replaced by other mechanisms. For this reason, we channeled a great deal of passion into conducting an extensive series of painstaking tests to fi nd out how to provide eff ective matting for UV-curable coatings.
The result: Our new matting agent ACEMATT® 3600 which, thanks to its special surface treatment, permits eff ective matting without solvents and so gives our cus-tomers more freedom in formulating matt, UV-curable coatings.
Curious about how exactly we went about things in our three examples? This issue deals with these topics in great detail. Happy reading!
ContactDr. Ulrich Küsthardt
We love your problems – at fi rst that might seem a strange thing to say. Evonik loves my problems? Do they want me to have problems? Far from it. But problems, challenges and solving them are part of everyday business. So it’s good to have a partner who’s committed to solving your problems and developing forward-looking solutions with commitment and creativity. That’s the core message behind “We love your problems”. For us, every problem is an opportunity to devel-op great solutions, solutions that are dovetailed to your needs because we’ve developed them together with you. Here are three examples to demonstrate just what we mean.
3
Smart Formulating Journal | Issue 9 | April 2012
Corrosion Protection Systems Environmentally Friendly Solutions with Novel Water-Borne Silane Sol-Gel Formulations and Water-Borne Coatings
Aluminium alloys are used extensively in the aerospace, automotive and construction industry because of their low density and high strength to weight ratio. Although some aluminium alloys can exhibit good corrosion resis-tance when exposed to the environment, the majority of aluminium alloys have to be protected against corrosion. Established surface pre-treatment processes, like chromat-ing and phosphating, are of high economic signifi cance. Due to high toxicity the use of chromium (VI) is no longer approved in the automotive and the electronic industries. Silane based systems are one of the most attractive alterna-tives since they are environmentally friendly.
Silanes were originally developed for adhesion promo-tion. They can improve the adhesion between inorganic fi llers and organic binders in composites. Silanes can be used as primers in formulations for better adhesion of polymers and coatings on inorganic substrates like met-als. Figure 1 shows the improved peel strength of a maleic acid gra� ed polyolefi n on an aluminium alloy primed with a silane solution.
Silanes are more and more used as additives in the fi eld of coatings or even as binders. Especially silane based water-borne sol-gel binders are of interest since they are environmentally friendly, storage stable, defi ned and off er interesting possibilities in the fi eld of corrosion pro-tection and metal treatment. Dynasylan® SIVO 160 is the latest development of such a silane based water-borne sol-gel system. Water-borne silane systems like Dynasylan® SIVO 160 are fully hydrolyzed, nearly VOC-free and contain reactive silanol groups which are stabi-lised. Therefore Dynasylan® SIVO 160 is a defi ned prod-uct with constant product quality and performance. The silanol groups can not just react with the metal substrate but also with each other in a condensation reaction. When the condensation reaction takes place, a dense network is formed at the surface of the aluminium substrate. In some cases the pure sol-gel system can form a stable layer and can give a good passive corrosion protection. It is a big advantage that formulations with Dynasylan® SIVO 160 can be used at low curing temperatures. The cured coat-ing layer can protect without top coat against corrosion, whilst simultaneously acting as an adhesion promoter when any subsequent coating is applied.
In most cases it is necessary to optimise the anticor-rosive properties and the overall performance by formu-lating water-borne sol-gel systems. Formulating know-how is helpful but in many cases water-borne sol-gel systems behave diff erently compared to organic coatings. Compatibility with additives, polymer dispersions, fi llers
and pigments can be a problem, especially when the pH of the water-borne sol-gel system (Dynasylan® SIVO 160 has a pH of 4 – 4.5) and e. g. the pH of the polymer dispersion does not match.
In the following example Figure 2 shows a diluted Dynasylan® SIVO 160 and a formulated Dynasylan® SIVO 160 solution used for the blank corrosion protection of the aluminium alloy 5005 used for construction applications. An untreated panel is used as control.
In Figure 2 it can be seen that after 1000 hours in the neutral salt spray test only the blank aluminium alloy 5005 showed corrosion. The samples treated with the diluted Dynasylan® SIVO 160 solution and the Dynasylan® SIVO 160 formulation showed less corrosion or no corrosion a� er 1000 hours in the salt spray test. In general, it can be stated for the aluminium alloy 5005:The diluted Dynasylan® SIVO 160 solution and the Dynasylan® SIVO 160 formulation do protect against cor-rosion. The Dynasylan® SIVO 160 formulation showed the best performance in the corrosion test.
Figure 1Peel strength: Aluminium stripes were primed with amino functional silanes. Primed stripes were bounded with maleic acid anhydride gra� ed PO at 160 °C. The adhesion was tested in a 180 ° peel test at 20 mm / min.
Blank
84
Medium force in N / 5 cm
Silane primer
120
Silane based water-borne sol-gel systems are usually applied as a thin layer in the nm range. In some cases the performance of such a thin layer can be limited. In these cases a top coat should be applied on the sol-gel layer. Since the cured sol-gel layer already protects the metal surface the layer thickness of the top coat can be reduced, depending on the performance that is needed.
If a coating with a high corrosion protection perfor-mance and vapour barrier is requested, water-borne poly-urethane (PUR) coatings can be used together with the sol-gel coatings as a sustainable solution. The additional corrosion protection can be important for corrosive sub-strates like the aluminium alloy 2024 T3. The excellent performance of such a combination is shown in Figure 3 a� er 200 hours in the humidity test.
The blank sample is discolored by corrosion products. Both, the Dynasylan® SIVO 160 treated plate without clearcoat as well as the aluminium plate coated only with a water-borne PUR clearcoat based on VESTANAT® EP-HP 2033 show corrosion. Perfect results could be obtained with the two layer coating consisting of environmentally friendly Dynasylan® SIVO 160 and a 5 µm layer of the water-borne PUR top coat.
Dynasylan® SIVO 160 provides excellent adhesion of the water-borne PUR coating to the aluminium substrate. The combination of Dynasylan® SIVO 160 and the water-borne clear coat results in a protective combination, that is resistant to both moisture and salt corrosion. It should be mentioned that the water-borne coating based on VESTANAT® EP-HP 2033 is displaying an excellent scratch resistance.
The market is looking for alternate corrosion pro-tection systems since chromate is being phased out and other surface pre-treatment processes still use aggressive media and chemicals with a high environ-mental impact. Novel water-borne silane sol-gel systems like Dynasylan® SIVO 160 are very promising solutions for such applications since they are nearly VOC-free and environmentally friendly. This kind of silane-based bind-ers can be modifi ed and formulated in many ways. It can be combined with environmentally friendly top coats such as the water-borne based on Vestanat® EP-HP 2033.
For commercial applications a detailed formulation development and stability testing is required.
Contact Dynasylan® Na� [email protected]
Contact Vestanat® Na� [email protected]
Contact Dynasylan® [email protected]
Contact Vestanat® [email protected]
Contact Dynasylan® [email protected]
Contact Vestanat® [email protected]
Figure 3Test results of coated aluminium alloy 2024 T3 a� er 200 hours in the humid-ity test (100 % RH, 40 °C). Procedure: Cleaning in a mild alkaline solution (60 °C), followed by by dip coating with a Dynasylan® SIVO 160 dilution: 15.0 % (w / w) Dynasylan® SIVO 160, 0.02 % (w / w) wetting agent all in dist. water; Curing at 60 °C for 10 minutes, layer thickness: 100 – 150 nm. Water-borne clear top coat: 19.95 % (w / w). Vestanat® EP-HP 2033, 0.15 % (w / w). BYK 341, 0.1 % (w / w). Reaxis C 333 (catalyst, Reaxis Ínc.), 79.8 % (w / w). dist. water. Coating was applied with a blade and cured at 80 °C for 10 min. Dry fi lm thickness: ~ 5 µm
200 Hours Humidity Test
Control SIVO 160SIVO 160 & coatingcoating
corrosion corrosioncorrosion no corrosion
Figure 2Test results of coated aluminium alloy 5005 a� er 1000 hours neutral salt spray test. Procedure: Cleaning in a mild alkaline solution (60 °C), followed by acid pickling followed by dip coating. Dynasylan® SIVO 160 dilution: 12,5 % (w / w) Dynasylan® SIVO 160, 0,02 % (w / w) wetting agent all in dist. water; Dynasylan®SIVO 160 formulation: 12,5 % (w / w) Dynasylan® SIVO 160, 0,02 % (w / w) wetting agent, 600 ppm Cr(III), all in dist. water. Curing for 10 mins at 80 °C; dry layer thickness: 100 – 200 nm
NSS 1000 Hours
Blank SIVO 160 dilutionSIVO 160
formulation
corrosion some corrosion no corrosion
4
Smart Formulating Journal | Issue 9 | April 2012
AEROSIL® Fumed Silica for Coating Defoamer
TableProcess Parameters Used to Prepare the Defoamer Formulation with Different Hydrophobic AEROSIL® Grades
Dispersing EnergyAEROSIL® concentration
Hydrophobic AEROSIL®fumed silica investigated
Low (Lab stirrer at 1000 rpm)
1 % by weight1.5 % by weight2 % by weight
AEROSIL® R 972AEROSIL® R 104 AEROSIL® R 974 AEROSIL® R 106 AEROSIL® R 805 AEROSIL® R 812 AEROSIL® R 812 S AEROSIL® R 202
Medium(Dissolver-blade at 2000 rpm)
High(Ultra-Turrax® at 10.000 rpm)
Silica in Coating DefoamerSurfactants are used in modern industrial coating for-mulations in order to facilitate dispersion and wetting of pigments and enhance incorporation of water-insoluble binders into water-borne paints. An undesired side eff ect of surfactants, however, is the stabilization of air bubbles, incorporated during the manufacture or application of coatings. Therefore, defoamers are o� en added in the prep-aration of coating formulations. For providing deaeration as well as defoaming eff ects, defoamers must exert inter-facial activity. A challenge remains: the defoamer applied needs to be partly incompatible with the coating formula-tion for the desired deaeration / antifoam eff ect, but must also be compatible enough with the respective binder sys-tem. Otherwise “fi sh eyes” and other failures may occur. The refore, several hydrophobic AEROSIL® fumed sil-ica grades were compared as part of a standard defoam-er formulation. The designation “R” in the AEROSIL® R grades indicates surface treated (hydrophobized) fumed silica. In all experiments a mixture of polyethersiloxanes (38 % by weight) and white oil Ondina® 913 (60 – 61 % by weight) was used as a base defoamer formulation. Diff erent hydrophobized AEROSIL® fumed silica types were incorporated as defoamer / deaerator booster. We addressed the question, which physico-chemical param-eter of the silica (e. g. surface area, silanol group density, C-content, hydrophobicity) infl uences the settling behav-
• Hydrophobic AEROSIL® fumed silica is an eff ective booster silica in defoamer formulations for waterborn coatings.• Increasing concentrations of hydrophobic AEROSIL® fumed silica products (1 to 2 % by weight) result in better
deaerator / defoamer performance.• AEROSIL® grades exhibit a better antisettling stability in deaerator / defoamer formulations when more dispersing
energy is applied in their manufacture.• All hydrophobic AEROSIL® grades are compatible with the tested polyurethane binder system.• Performance and compatibility of hydrophobic AEROSIL® grades with the examined acrylate / methacrylate and
polyvinyl acetate binder systems improve with increasing hydrophobicity.
ior, the performance and fi nally the compatibility the most.
It is well known that the incorporation of fumed silica into a defoamer formulation may be critical with regard to silica concentration and the dispersing energy. In order to limit the number of defoamer formulations and the respective application tests a program was set up accord-ing to a design of experiments (DoE). Microscopic and rheological evaluations accompanied the settling behav-ior of the respective AEROSIL® fumed silica product in the defoamer formulation. In a second step, the defoamer
formulations were applied to three diff erent binder sys-tems. Air content was evaluated gravimetrically and fi nal-ly the fl ow out test on a polyethylene covered slope was examined for compatibility, e. g. fi sh-eyes, spots or other failures.
Sedimentation Stability of Hydrophobic AEROSIL® Fumed Silica in Defoamer FormulationsInitially the focus was on the sedimentation stability of hydrophobic AEROSIL® fumed silica in the defoamer for-mulation. Eight diff erent hydrophobic AEROSIL® grades were dispersed into the defoamer formulation at three levels of dispersing energy and in three diff erent concen-trations (see table).
The combined results of the visual, microscopic and rheological evaluations were as expected. They showed that the highest sedimentation stability of the defoamer was achieved when using
a) the highest dispersing energy (10 000 rpm, Ultra-Turrax®) and
b) the highest AEROSIL® concentration (2 % by weight).
The sedimentation stability correlated well with the hydrophobic nature of the respective fumed booster silica. AEROSIL® R 972, AEROSIL® R 104 and AEROSIL® R 974 tend to sediment easier (relative score about 70) in the
SILIKOPUR® 8080 – an Innovative Combination of Polyurethane and Silicone!
SILIKOPUR® 8080 is a one-pack, silicone-modifi ed poly-urethane manufactured using a targeted combination of silicone and polyurethane components. While polyester polyol is used in the manufacture of conventional PU dispersions, hydroxyfunctional organosiloxane is used in the synthesis of SILIKOPUR® 8080. This gives the product the unique properties of silicone-containing compounds.
Coatings based on SILIKOPUR® 8080 are used sub-stantially on leather, textiles, wood and plastics. They distinguish themselves principally by a high elas-
ticity which is retained even at low temperatures. The coatings also exhibit hydrophobic characteristics and a non-stick eff ect. Used in combination with acrylic binders, the product can improve abrasion resistance. SILIKOPUR® 8080 can be diluted with water and is air-drying.
ContactDr. Sascha Herrwerth
5
Smart Formulating Journal | Issue 9 | April 2012
used standard defoamer formulation, whereas the more hydrophobic fumed silica products AEROSIL® R 812 S and AEROSIL® R 202 exhibited a better antisettling behavior (relative score about 80, see fi gure 1).
Figure 1Sedimentation Stability of Different Hydrophobic AEROSIL® Fumed Silica Grades
60 70 80 90
AEROSIL® R 972
AEROSIL® R 104
AEROSIL® R 974
AEROSIL® R 106
AEROSIL® R 805
AEROSIL® R 812
AEROSIL® R 812S
AEROSIL® R 202
Incr
easin
g H
ydro
phob
icity
Relative Score
Figure 2Performance and Compatibility of Hydrophobic AEROSIL® Grades in Different Binder Systems
0,8 0,9 1
AEROSIL® R 972
AEROSIL® R 104
AEROSIL® R 974
AEROSIL® R 106
AEROSIL® R 805
AEROSIL® R 812
AEROSIL® R 812S
AEROSIL® R 202
Mowilith 7717 APU 1035 AirFlexCEF 10
Incr
easin
g H
ydro
phob
icity
Relative Score
mixture was stirred for one minute at 3000 rpm (labora-tory stirrer) in order to allow air introduction, followed by immediate gravimetrical estimation of the air content and subsequent fl ow-out test for compatibility evaluation and scoring.
The defoamer / deaerator performance and compatibil-ity of the respective defoamer formulation in three diff er-ent dispersion systems systems
a) Acrylate / methacrylate (Mowilith® 7717, Celanese)b) Polyurethane (APU® 1035, Alberdingk-Boley)c) Polyvinylacetate (Airfl ex® CEF 10, now Wacker)
was then evaluated and scored. The performance / com-patibility in the polyurethane-dispersion was found to be very good with all of the tested defoamer formu-lations and hydrophobic fumed silica AEROSIL® grades (APU® 1035, purple columns, all score close to 1, see fi gure 2).
In case of the acr ylate / methacr ylate binder (Mowilith® 7717, grey columns, score 0.85-0.93) as well as with the polyvinylacetate – binder system (Airfl ex® CEF 10, light purple columns, score 0.89-1.0) the hydrophobic AEROSIL® grades exhibited a broader range in their performance and compatibility with the binder system. It could be seen that the less hydrophobic AEROSIL® products AEROSIL® R 972, AEROSIL® R 104 and AEROSIL® R 974 are less compatible with these binder systems than the more hydrophobic grades, AEROSIL® R 812 S, AEROSIL® R 8200 and AEROSIL® R 202.
Although the results clearly indicate that in the giv-en formulation higher hydrophobic AEROSIL® contents provide better results, it should be mentioned that it is diffi cult to predict the behavior of fumed booster silica in other coating defoamer formulations with regard to settling and compatibility. Hence it is known that in other defoamer base formulations, also less hydrophobic AEROSIL® R 972 and AEROSIL® R 974 are used success-
fully in coating defoamer formulations.
ContactDr. H.-W. Wollenweber
Performance and Compatibility of Hydrophobic AEROSIL® Grades The defoamer formulations above were added at three diff erent defoamer concentrations (0.1 %, 0.175 %, and 0.25 % by weight) to the respective binder system and the
UV Coatings: as Matte as it GetsWhen one thinks of eco-friendly coatings, UV-curable coatings immediately spring to mind. Traditional uses are for wood and furniture lacquers and printing inks. As we know, application on plastics and metal substrates is also signifi cant for coatings such as these.
The gloss of such UV coatings should, of course, be able to be varied over a large range from high to low gloss including dull matte finishes. Strong matting is often required, but dull matte fi nishes are particularly diffi -cult to achieve with UV coatings. Increasing the matting agent content usually leads to undesirable higher viscosi-ties, yield point anomalies and thixotropic eff ects and, consequently, problems during the application process (e. g. with roll units).
The quality of the coatings surface also leaves much to be desired because of fl ow problems or air inclusions.
The solution:
optimal wetting of the surface of matting agents
TEGO® Dispers 688, a new polymeric wetting and dis-persing additive from Evonik, has been developed specifi -cally for optimal wetting and stabilization of matting agent surfaces. TEGO® Dispers 688 enables the formulator to signifi cantly lower the viscosity of the matte formulation. The yield point of such formulations is also lowered and
thixotropic eff ects reduced. This results in good matting and problem-free application. Lowering the yield point positively aff ects the fl ow and degassing of the coating fi lm. TEGO® Dispers 688 is highly eff ective on the most diverse matting agents in UV formulations based on all the common types of oligomers.
TEGO® Dispers 688 off ers the positive eff ects men-tioned above. It also suppresses the undesirable reglossing (gloss-up) of the coating which occurs with many other wetting and dispersing additives.
ContactHeike Semmler
6
Smart Formulating Journal | Issue 9 | April 2012
Widening the Scope for Matting Solvent-Free UV-Cured Coatings
Model for insufficient mattingEarlier ”gel point” = high shrinkage efficiency factor= insufficient roughening
UV radiator
Model for effective mattingLater ”gel point” = low shrinkage efficiency factor= sufficiently high roughening
UV radiator
Reaction start
Conveyor speed: 6m/min = 3 sec exposure
”Gel point” Reaction end
30 cm
Figure 3When the gelling point is reached prematurely, this results in an inadequate poor degree of coarsening (model pictured at top). A later gelling point allows time for sufficient coarsening to transpire (model pictured at bottom).
At which point in time the gelling point is reached depends on a number of thermodynamic and reaction_kinetic factors. The other components in the formulation (acrylate oligomers; acrylate monomers and photoinitia-tors) therefore also have a substantial impact on the mat-tability of UV-cured coatings.
Number of Double Bonds Plays an Important RoleThe existence of complex reciprocal dependencies means it is diffi cult to make any defi nite assertions regarding the mattability of oligomers. Evonik has, however, been able to prove that the double-bonding density, which, in turn, is contingent on functionality and molecular mass, is of particular signifi cance. Generally speaking, we can say that the higher the double-bonding density of the oligo-mers, the greater the mattability of the coating.
Formula for Calculation of the Double-Bonding Density
DB-Density = funtionalityt [DB / Mol]
x 1000 [g / kg Oligomer] = x 1000 [g / kg Oligomer] = [DB]
relative molar mass [g / Mol] x 1000 [g / kg Oligomer] = relative molar mass [g / Mol] x 1000 [g / kg Oligomer] =
[kg Oligomer]
Experiments with diff erent monomers have shown that their contribution to the matting eff ect depends primarily on their molecular form and turnover rate during polym-erization.
The photoinitiator also infl uences the mattability of UV-cured coatings chiefl y through its absorption maxima.
The actual curing process provides additional scope for reducing the shine in a coating fi lm, with parameters such as the type of light source and its emissions spectrum, the intensity and exposure time, the geometry of the lamps used, the ambient temperature and type of substrate all fi guring into the equation. Evonik’s application engineers have looked at these variables, too.
Coating formulation continues to be predominantly a matter of employing experience and intuition. Evonik’s analyses do, however, show that it is possible to expressly fi ne-tune and coordinate the pertinent process and for-mulation parameters and thus signifi cantly improve the degree of control employable in matting UV-cured coat-ings. The new ACEMATT® 3600 now aff ords formulators a greater array of options for the matting process.
ContactReinhard Behl
Rüdiger [email protected]
It is relatively easy to produce a matt fi nish in conventional, solvent-based coatings as opposed to UV-cured coatings. In extensive testing which has seen it accomplish groundwork in this fi eld, Evonik has come up with a more eff ective way of matting these latter types of coating. The resulting product is a new matting agent, ACEMATT® 3600, with a special surface treatment. This product now broadens the options available for the formulation of matt UV coatings.A Simple Model for a Complexity of CorrelationsApplication engineers at the Evonik have developed a model for matting UV-cured coatings. Their model illus-trates how the non-materialization of film shrinkage caused by the absence of solvents can be off set by other mechanisms.
The fi rst parameter which the developers examined was particle size of the matting agent. They looked at two conventional silicas used to create a matt fi nish. These silicas had mean agglomerate particle sizes of 4.5 µm and 14.5 µm (in ACEMATT® OK 607and ACEMATT® HK 450, respectively). Using this simple model which covers the whole spectrum of particle sizes used in silica-based mat-ting agents, it is possible to qualify the impact various par-ticle sizes have. In this model, same-size spherical par-ticles in the highest possible packing density represent the silica particles. The agglomerates are evenly distributed throughout the liquid coating, creating a matting–agent matrix which does not shrink as much as the binder–agent matrix surrounding it does during the curing process. The so-called volume shrinkage of coating during curing is caused chiefl y by the binding agent. The idea the coat-ing experts had was that it ought to be possible to control matting to some extent by manipulating the particle size in the matting agent.
Small Particles for More Effi cient Matting in Thick-Layer UV CoatingsAccording to the spherical-particles model, if a thick UV-cured coating (< 20 to 25 g / m2) contains a matting agent whose particles are relatively large (14.5 µm), the volume shrinkage this produces during curing will result in the surface of the coating exhibiting only weakly pronounced, long-wave structures. The surface will be only-moderate-ly roughened and therefore exhibit only a minimal degree of matting.
In contrast, fi ner-particle matting agents containing particles of 4.5 µm in size will produce a coating-fi lm surface with a pronounced short-wave structure which is ideal for the strong diff usion of incident light and thus produces a high degree of matting (Fig. 1). The result is a low level of shine at a 60 ° angle.
On the whole, the testing shows that fi ne silica par-ticles with mean agglomerate particle sizes of < 5.5 µm are excellently suited for matting thick-layer UV coatings.
Coarse particle matting agent ACEMATT® HK 450/d50 = 14.5μm
Fine particle matting agent ACEMATT® OK 607/d50 = 4.5μm
Derived from modelHeight difference appr.: 2.0μmWith low roughening and high gloss at both measurement angels
Values from actual practice60°-reflectometervalue: 46.185°-reflectometervalue: 86.0Max. roughness profile height Rz: 0.77μmArithm. mean roughness value Ra: 0.08μm
Devided from modelHeight difference appr.: 2.0μmwith higher rougheningLow gloss at 60° measurement angelHigh gloss at 85° measurement angel
Werte aus der Praxis60°-reflectometervalue: 22.685°-reflectometervalue: 77.8Max. roughness profile height Rz: 1.20μmArithm. mean roughness value Ra: 0.14μm
Figure 1The surface structures of a thick coating film.
Large Particles for Thin LayersWhen it comes to the matting of thin layers, coating for-mulators only gain limited benefi t from polymerization induced volume shrinkage since the layers are simply not thick enough. For thin layers, therefore, coarser-particle silica will always be a better choice than fi ne-particle acid if the particle size approximately matches that of the layer thickness.
For this, too, the devised model provides an expla-nation: The large particles create a highly pronounced structure (that is, a signifi cant degree of coarseness) on the fi lm surface, while fi ne-particle matting agents create minimally pronounced structures on thin layers, resulting in barely any diff usion of incident light (Fig. 2). What this means for thin coating layers is that the mean agglomerate of the matting agent will ideally be 0.5 to 1 times the size of the coating-fi lm thickness.
Coarse particle matting agent ACEMATT® HK 450/d50 = 14.5μm
Fine particle matting agent ACEMATT® OK 607/d50 = 4.5μm
Derived from modelHeight difference: > 2.0μmwith high roughening and low gloss at both measurement angels
Values from actual practice60°-reflectometervalue: 31.085°-reflectometervalue: 49.2Max. roughness profile height Rz: 3.92 μmArithm. mean roughness value Ra: 0.21μm
Derived from modelHeight difference: < 1.0μmwith low roughening and high gloss at both measurement angels
Values from actual practice60°-reflectometervalue: 46.885°-reflectometervalue: 83.8Max. roughness profile height Rz: 0.86 μmArithm. mean roughness value Ra: 0.08 μm
Figure 2The surface structure of a thin coating film.
New Matting Agent Widens Processing WindowPractice corroborates the test results, as Fig. 1 and 2 illus-trates. Matting can be better produced in thick coating fi lms using fi ne-particle silicas, and coarse-particle silica is better used to create this eff ect in thin coating layers.
It also becomes clear that the new ACEMATT® 3600, developed specifi cally for creating matt fi nishes for UV-cured coatings and post-treated with polydimethylsiloxan (PDMS), has a signifi cantly higher matting eff ect across practically all layer densities. Given that it was also found to have a positive infl uence on the matting agent’s rheo-logical properties and can therefore be added to the coat-ings in a higher concentration, formulators now have a much broader application window at their disposal.
Diff erent Time Sequences in The Polymerization Process Aff ect The Degree of GlossAnother essential factor in matting is the time sequence employed in the polymerization process to the point of gelling (one of the defi ned time points in the processing schedule). It is at this point in time that polymerization of the binding agent has progressed to the stage that the silica and binding-agent matrixes proceed to jointly shrink further. From the point of gelling onward the agglomer-ates of the matting agent are fi xed in the emerging poly-mer network and can thus no longer contribute to any further coarsening. The later the gelling point is reached, the more pronounced the matting eff ect will be (Fig. 3).
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Smart Formulating Journal | Issue 9 | April 2012
TEGO® AddBond – the Multitasking Adhesion Promoter!
TEGO® Airex 990 and TEGO® Airex 991Modern, solvent-free deaerators for the next generation of high-solids coatings
The TEGO®AddBond product group is an excel-lent choice for optimizing the adhesion and cohesion of coatings with numerous substrates and binders. TEGO® AddBond products are specialized polyester resins precisely tailored by the selective use of suitable com-ponents. The tailored molecules have an optimized den-sity of hydroxy and carboxy functionality to meet user requirements in solventborne, high-solids and water-borne systems. Additional properties such as gloss, hard-
Modern high-solids coatings are formulated with ever greater solids content. This frequently leads to the problem of foam during application. Modern 2-pack poly-urethane and 2-pack epoxy formulations, in particular, o� en exhibit micro- and macro-foam during airless or air-assisted airless spray applications. For other applica-tion processes too, fi nding a really eff ective and suffi cient-ly compatible deaerator is frequently a challenge for the formulator.
ness or fl exibility and broad compatibility in diff erent systems make them multifunctional. As they can be used in water-borne systems or low-VOC formulations, the TEGO® AddBond product group also makes a lasting con-tribution to modern eco-friendly coatings.
ContactHeiko Alzer
With TEGO® Airex 990 and TEGO® Airex 991, Evonik has developed simultaneously two new deaerators to meet these challenges. Achieving an optimum fi nish with high-solids formulations is no problem even in high fi lm build coatings.
Both deaerators are solvent-free and contain 100 % active substance. This gives the formulator greater free-dom in the choice of type and amount of solvent in the coating.
As a compatible deaerator, TEGO® Airex 990 is par-ticularly suitable for use in non-pigmented high-solids, high gloss systems. It can also be used in pigmented or matte paint formulations. Its strength is the balance between good compatibility and effective deaeration. TEGO® Airex 990 is suitable for all types of spray application.
TEGO® Airex 991 is a highly effective deaerator for pigmented high-solids coatings. Thanks to its out-standing eff ectiveness against micro- and macro-foam,TEGO® Airex 991 can be used in a wide range of high-sol-ids systems with a special emphasis on airless, air-assisted airless and roller application.
Both new products are easy to handle, easy to mix in and do not require special labeling.
ContactCornelia Alzer
Heike [email protected]
• TEGO® AddBond LTH (100 % solid resin) is used in solventborne systems for optimizing hardness, gloss and adhesion on metals.
• TEGO® AddBond LTW (60 % in xylene, or TEGO® AddBond LTW-B 60 % in butyl acetate). As a so� , fl exible polyes-ter resin, it is used to improve adhesion onplastics and metals.
• TEGO® AddBond HS has a property profi le comparable to that of TEGO® AddBond LTW, but is supplied as a 75 % solution in butyl acetate. It is therefore preferred in high-solids coatings.
• TEGO® AddBond DS 1300 is an aqueous dispersion and therefore improves the adhesion on metals and plastics as well as the fl exibility of air- and heat-drying water-borne coatings.
• TEGO® AddBond 1270 (70 % in sec-butanol) substantially improves the adhesion on metals and plastics of solvent-borne and, a� er neutralization, of water-borne coatings.
Figure 1Transparent high-solids coating, spray-applied on black PMMA a) with TEGOAirex 990 and b) with reference deaerator
a) b)
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Smart Formulating Journal | Issue 9 | April 2012
Liquid Silica Nanocomposites from Evonik – Scratch Resistance and Transparency for Coatings SystemsLiquid silica nanocomposites from Evonik are used primarily where coatings are required to exhibit high scratch and abrasion resistance without sacrifi cing transparency. Also, these products should be easy to formulate. Furthermore, secondary properties such as barrier eff ect, reduced shrinkage during curing and improved adhesion on substrates with hydroxyl function can be achieved in various coatings systems without compromising the degree of gloss. The properties can only be achieved by conventional means by using several layers.
Manufacture of silica nanocompositesUsing a modifi ed sol-gel process, it is possible to manufac-ture composites from silica nanoparticles and organic res-ins which, despite being 50 % w / w fi lled, are water white.
Starting from water glass, spherical silica nanopar-ticles, approximately 20 nm in diameter and with a very narrow size distribution, can be cultured in an aqueous environment.
These particles then have their surfaces modifi ed to permit a stable transfer into their future organic matrix. The results are transparent products that do not exhibit any sedimentation.
Improving properties with silica nanocompositesSilica nanocomposites should be regarded as an additive to the binder in a coating formulation.
In addition to the main property of scratch and abra-sion resistance while maintaining transparency, silica nanocomposites improve other properties of the coating. Thus, they reduce shrinkage during curing and improve barrier eff ects.
The particles in the cured fi lm are statistically distrib-uted, i. e. the average distribution is identical at the sur-face, in the middle and at the bottom.
Nanocomposite particle distribution
This is quite diff erent from surface active products such as waxes or silicone oils which are only eff ective at the coating / air interface and thus have only a temporary eff ect on scratch and abrasion resistance.
Silica nanocomposites, in contrast, off er permanent protection as they are fi rmly bound in the cured fi lm matrix. Because they are distributed throughout the whole fi lm, the initial recommendation is 5 to 10 % w / w relative to the solids of a coating formulation.
The liquid nanocomposites from Evonik also have the advantage that they only cause a slight increase in the viscosity of the coating formulation. This is achieved by customized surface modifi cation of the nanoparticles.
On substrates such as glass and aluminum, the glassy nanoparticles improve adhesion. This eff ect is utilized in, for example, printing on high quality glass bottles.
Silica nanoparticles are also suitable for applications where a barrier effect is required, especially where excellent transparency is needed. The barrier eff ect in an organic coating is increased by the inorganic silica par-ticles. Diff usion of oxygen or water vapor is thus signifi -cantly lower when compared to an unmodifi ed clearcoat.
The degree of gloss of the formulation is not aff ected by the silica nanoparticles. Unlike surface waxes, which are added as matting agents, the nanoparticles do not settle out on the surface but are, as already described, distributed statistically throughout the entire fi lm. It is thus possible to obtain coatings with improved hardness, scratch and abrasion resistance without being restricted by considerations on the degree of gloss.
Use of silica nanocompositesIncorporation of the liquid composites is easy. Like stan-dard binders, the products are thoroughly stirred in together with the main binder at the start of the produc-tion process. Dispersing or bead milling is unnecessary.
Moderately polar solvents such as xylene or toluene should not be used alone in formulations. These solvents are, however, generally very compatible when used in blends with popular solvents such as esters, ketones and alcohols.
Certain additives can result in incompatibilities with silica nanocomposites. These manifest themselves in, for example, agglomeration, fl occulation or increased viscos-ity of the coating formulation.
To save laboratory time when developing coatings with silica nanocomposites, compatibility lists are available from us on request for the additives most commonly used with NANOCRYL®, NANOPOX® and NANOPOL®. These lists give recommendations for the compatibility of addi-tives with the silica nanocomposites in terms of short- and long-term shelf-life.
Silica nanocomposites for various coatings systemsOptimized silica nanocomposites have been developed by Tego for the diff erent curing mechanisms in coatings.
NANOCRYL®, a range of silica nanocomposites in vari-ous commonly used UV-curable acrylate monomers, has Evonik been specially developed for radical-curing UV coatings.
Product Overview NANOCRYL®
Name MonomerSiO2-con-tent[% w / w]
Viscosity,25 °C
NANOCRYL® C 130
Trimethylolpropane-formalacrylate
50 275 mPa•s
NANOCRYL® C 140
Hexanedioldiacrylate 50 175 mPa•s
NANOCRYL® C 145
Tripropyleneglycoldi-acrylate
50 200 mPa•s
NANOCRYL® C 150
Trimethylolpropane-triacrylate
50 3.3 Pa•s
NANOCRYL® C 153
Ethoxylated trimethyl-olpropanetriacrylate
50 1.0 Pa•s
NANOCRYL® C 155
Propoxylated glyceri-netriacrylate
50 1.75 Pa•s
NANOCRYL® C 165
Alkoxylated pentae-rythritoltetraacrylate
50 2.5 Pa•s
Listing status of individual products available on request.
NANOPOX® materials are manufactured from epoxide resins and suitable reactive diluents.
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Smart Formulating Journal | Issue 9 | April 2012
High Technology in the Store CupboardDYNAPOL® Specialty Coating Resins for Exterior and Inte-rior Protection of the Classic Food CanSaturated copolyesters have been used for many years as binders in the area of packaging. The reason is the “mod-ular construction system” of polyester chemistry: By an appropriate choice of monomers and their quantitative assembly in the formulation of the polyester, the customer gets exactly the properties he wants. Evonik currently has about 35 monomers available for synthesis into custom-ized polyesters. One outstanding feature here is the bal-ance between fl exibility and hardness that can be achieved by adjusting the formulation. In addition, the copolyesters are odorless and tasteless, and therefore suitable even for packaging with direct food contact.
Frequent changes and new trends in the packaging market have resulted in polyesters, of all the available binders, increasingly coming into focus due to their excel-lent properties. Interest in, and demand for, polyesters in the packaging market has risen signifi cantly. Under the DYNAPOL® brand name, Evonik markets copolyesters used as binders in fl exible packaging (fi lm primers, print-ing inks), coil coatings (facade elements, refrigerators), and can coatings (food cans, metal packaging).
On the subject of cans, it is interesting that no less a personage than Napoleon announced a competition about 200 years ago to fi nd a process for preserving food. The
winning entry, based on the idea of sealing food in airtight containers, came from a Parisian confectioner. The thin metal shell is now well established in many application areas, from the preservation of food and drink to the stor-age of chemical products. The can is tough, heat resistant, 100 percent recyclable, and to be found in every store cupboard.
The biggest challenge in the area of can coating is the internal coating of food cans, particularly at the stage where pre-coated metal plate is shaped into can bodies. The coating must be fl exible enough to withstand the shaping process without damage. A typical tin can con-tains several coating layers, up to three outside and one inside. The exterior layers protect the can from corro-sion and the color printing of the advertising space from scratches. “In production, coatings are fi rst applied on thin tinplate and stoved. The body and lid of the can are then stamped and formed from the coated metal sheet. The coating must be suffi ciently fl exible or it will crack and fl ake off . If it’s too fl exible, on the other hand, it doesn’t off er enough hardness and protection,” says Rainer Spitt-ka of Technical Service, Pre-Coated Metal.
Evonik’s polyester resins, designed with just this bal-ancing act in mind, off er both optimal protection and high fl exibility. For food cans, the requirements on the exterior
coating are particularly high; once fi lled, the cans face the next test of their durability: sterilization. To preserve the food, the packaging must be treated at 130 degrees Celsius and high pressure in the sterilization chamber. Only if the exterior coating has come through this step undamaged is the can ready for sale. And DYNAPOL® is useful inside the can as well, because most foods contain ingredients that attack tinplate, such as vinegar, lactic acid, oils, and salts. If the can contains sauerkraut or chilli, for example, it must also be protected from the inside. The inner coat-ing layer prevents the acids in the food from attacking the metal, and metal particles from entering the food.
The development, testing, and statutory approval of suitable coating systems for food contact applications takes several years. This sensitive field of application therefore uses mainly “classics” such as the high molec-ular weight DYNAPOL® L 912 and DYNAPOL® L 952 grades. However, relatively new products such as the medium molecular weight DYNAPOL® LH 815-05 and DYNAPOL® LH 318-02 grades have also been successfully launched on the market.
ContactRainer Spittka
Evonik’s Coatings & Additives Business Unit ensures reliable protection against corrosion, wear, and scratching. Under the DYNAPOL® brand name it markets specialty coating resins that protect metal packaging both externally and internally.
Product Overview NANOPOX I
Name
SiO2-content [% w / w] Base resin
EEW[g / equiv.]
Viscosity25 °C
Charac-terization
NANOPOX® C 450
40 DGEBA 295 60,000mPa•s
aromatic
NANOPOX® C 460
40 DGEBA/ DGEBF
290 45,000mPa•s
aromatic,crystal-lization-free
Listing status of individual products available on request.
These NANOPOX® products can be heat-cured anhy-drously, room-temperature cured with amines, or force cured.
Product Overview NANOPOX II
Name
SiO2-content [% w / w] Base resin
EEW[g / equiv.]
Viscosity25 °C
NANOPOX® C 620
EEC Cycloaliphatic epoxy resin for cationic UV-curing
40 4.0 Pa•s
Listing status of individual products available on request.
The product NANOPOX® C 620 is suitable for cationic UV-curing. NANOPOL® is a solvent-based product which is universally applicable. It is equally suited for use in 1-pack stoving enamels and in 2-pack PUR or UV coatings.
Product Overview NANOPOL
Name Solvent SiO2-content [% w / w]
Viscosity25 °C
NANOPOL® C 764
Methoxypropylacetate 50 < 50 mPa•s
NANOPOL® C 784
N-butylacetate 50 < 50 mPa•s
Listing status of individual products available on request.
ContactMarco Heuer
Dynapol in Every Layer
1 Internal seam of the can: A special DYNAPOL® grade covers the weld seam of the can.
2 Interior coating of the can: This protective layer prevents acids in the food from attacking the metal, and metal particles from entering the food.
3 Stamping enamel: The clear white coating protects the metal against corrosion and serves as a primer for pin-sharp printing.
4 Printing can be in any desired color.
5 Overprint varnish protects the print during sterilization and later against abrasion and scratching.
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Smart Formulating Journal | Issue 9 | April 2012
10
DatesSmart Formulating Trade Fair Appearances 2012
08 – 10 May 2012American Coatings Show | USA, Indianapolis
13 – 15 September 2012Paintistanbul | Türkei, Istanbul
02 – 04 October 2012EuroCoat | Spanien, Barcelona
25 – 27 October 2012China Adhesives | China, Shanghai
28 – 30 November 2012ChinaCoat | China, Guangzhou
ImprintEditorEvonik Industries AGRellinghauser Straße 1 – 1145128 Essen, Germany
Editorial teamRainer Lomölder Wernfried Heilen, Wilfried Robers, Torsten StojanikContact: [email protected]
Layout / DesignLiebchen+Liebchen Kommunikation GmbH www.LplusL.de Frankfurt am Main, Germany
Printed in Germany
American Coatings Show 2012 in IndianapolisNew venue – new look – new concept
At this year’s American Coatings Show, which is being held in Indianapolis for the fi rst time, Evonik will be posi-tioning itself as a creative problem-solver dedicated to addressing challenges faced by its customers. “We love your problems” is the slogan for the exhibit. “With this message, we want not only to advertise ourselves, but also to open up a dialogue with our customers and discuss the challenges that may be awaiting them in the future,” says Dr. Klaus Engel, Chairman of the Executive Board of Evonik Industries AG.
Visit us at ACS Visit us at ACS
Stand 2000
Evonik’s exhibit, which will be almost 50 percent larg-er than in the past, will showcase products and solutions for the coatings market, including some developed in col-laboration with customers. As well as counters and tables for discussion with customers, there will be a lounge area where our visitors can relax for a while. In each area, products will be presented individually using iPads.
We look forward to discussing new trends and our product innovations for the coatings market with custom-ers. And we also look forward to bringing home a range of new problems to be solved. We love your problems.
ContactHolger Maasewerd
